Abnormality detecting apparatus for detecting abnormality at interface portion of contact arm

ABSTRACT

An abnormality detecting apparatus includes an imaging device for obtaining image data of a TIM, a failure detecting section for detecting appearance failures of the TIM on the basis of the image data of the TIM obtained by the imaging device, and a determining device for determining whether an abnormality occurs at the TIM on the basis of a detection result by the failure detecting section.

TECHNICAL FIELD

The present invention relates to an abnormality detecting apparatus fordetecting an abnormality at an interface portion of a contact arm whichpresses a device under test onto a contact portion of a test head in anelectronic device testing apparatus, an electronic device testingapparatus and an electronic device testing system with the same, and anabnormality detecting method.

BACKGROUND ART

In production processes for various kinds of electronic devices(hereinafter also representatively referred to as “IC devices”) such assemiconductor integrated circuit devices, there is used an electronicdevice testing apparatus for testing performances and functionalcapabilities of IC devices.

As a handler which forms an electronic device testing apparatus fortesting IC devices requiring relatively short testing time such as SoC(System on Chip) and the like, a type that a contact arm holds each ICdevice by suction one-by-one and presses the IC device onto a socket ofa test head is known (for example, see Patent Document 1).

The contact arm of such handler has a pusher for pressing an IC deviceonto the socket, and the pusher is provided therein with a temperaturecontroller configured with a heater, a cooler, and the like in order tocontrol the temperature of the IC device. In addition, there is a casethat a TIM (Thermal Interface Material) formed of, for example, aluminumfoil or the like is attached to an front end of the pusher so that acontact performance between the pusher and the IC device is improvedthereby decreasing the thermal resistance therebetween.

Because the TIM is subjected to a repetition of being close contact withan IC device and being removed therefrom while the contact arm holds ICdevices by suction, there occur scars and defects on the surface of theTIM or foreign particles such as dusts attach to the surface.Consequently, a TIM which has been contacted with IC devices at apredetermined times is to be newly changed.

However, if the pusher has an front end with insufficient flatness orthe contact arm is inclined, scars and defects on the TIM may besignificantly increased before completing the predetermined times. Also,if IC devices have burrs or the electronic device testing apparatus isused in a dusty environment, considerable amount of foreign particlesmay attach to the TIM before completing the predetermined times.

In the case that such an abnormality occurs in the TIM, the thermalresistance between the pusher and the IC device is insufficientlydecreased. Therefore, there probably occur problems that it is notpossible to control the temperature of the IC device with accuracy andthat it takes a long time to reach the IC device to a set temperature.

[Patent Document 1] Japanese Patent Publication (A) No. 2002-5990

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

The problem to be solved by the present invention is to provide anabnormality detecting apparatus capable of maintaining a good heatconductivity between a contact arm and a device under test, anelectronic device testing apparatus and an electronic device testingsystem with the same, and an abnormality detecting method.

Means for Solving the Problem

(1) To achieve the above object, according to a first aspect of thepresent invention, there is provided an abnormality detecting apparatusfor detecting an abnormality of an interface portion with a device undertest, the interface portion being provided with a contact arm forpressing the device under test onto a contact portion of a test head inan electronic device testing apparatus for testing the device undertest, the abnormality detecting apparatus comprising: an obtaining meansfor obtaining an appearance information of the interface portion of thecontact arm; a failure detecting means for detecting an appearancefailure of the interface portion on the basis of the appearanceinformation obtained by the obtaining means; and a determining means fordetermining whether the abnormality occurs at the interface portion onthe basis of a detection result by the failure detecting means (seeclaim 1).

Although not particularly limited in the above invention, preferably theinterface portion includes a thin-plate-shaped member or athin-film-shaped member provided on a front end of the contact arm, or aliquid applied on the front end of the contact arm (see claim 2).

Although not particularly limited in the above invention, preferably thedetermining means has: a classifying section for classifying theappearance failure detected by the failure detecting means into aplurality of failure categories on the basis of predetermined criteria;a counting section for counting a number of failures in each of thefailure categories and generating an actual count number for eachcategory; and a comparing section for comparing the actual count numbergenerated by the comparing section with a reference count number foreach category with respect to each of the failure categories, anddetermining whether the abnormality occurs at the interface portion onthe basis of the comparison result, the reference count number beingpreliminarily set as a reference number of failures in each of thefailure categories (see claim 3).

Although not particularly limited in the above invention, preferably thecomparing section determines that the abnormality occurs at theinterface portion when the actual count number is larger than thereference count number with respect to at least one of the failurecategories (see claim 4).

Although not particularly limited in the above invention, preferably theabnormality detecting apparatus further comprises an alarming means forinforming that the interface portion is abnormal or informing of afailure category which is a cause for an occurrence of the abnormalityat the interface portion when the comparing section determines that theabnormality occurs at the interface portion (see claim 5).

Although not particularly limited in the above invention, preferably theobtaining means includes an imaging means for picking up an image of theinterface portion (see claim 6).

Although not particularly limited in the above invention, preferably thefailure detecting means specifies, as the appearance failure area of theinterface portion, an area having a predetermined contrasting densitydifference from a background in a real image information picked up bythe imaging means (see claim 7).

Although not particularly limited in the above invention, preferably theclassifying section classifies the appearance failure area into any oneof the failure categories on the basis of at least one of contrastingdensity, shape, or position of the appearance failure area specified bythe failure detecting means (see claim 8).

Although not particularly limited in the above invention, preferably theabnormality detecting apparatus further comprises a memory means formemorizing a reference image information of the interface portion whichis preliminarily picked up by the imaging means as a reference, and thefailure detecting means generates a differential image information byperforming a differential processing between the real image informationpicked up by the imaging means and the reference image informationmemorized in the memory means and specifies, as the appearance failurearea of the interface portion, an area having a predeterminedcontrasting density difference from a background in the differentialimage information (see claim 9).

Although not particularly limited in the above invention, preferably theclassifying section classifies the appearance failure area into any oneof the failure categories on the basis of at least one of contrastingdensity, shape, or position of the appearance failure area in thedifferential image information (see claim 10).

Although not particularly limited in the above invention, preferably theabnormality detecting apparatus further comprises an irradiating meansfor irradiating the interface portion (see claim 11).

Although not particularly limited in the above invention, preferably theirradiating means is capable of irradiating the interface portion withvisual light ray or ultraviolet ray, and the imaging means is capable ofreceiving visual light ray or ultraviolet ray (see claim 12).

Although not particularly limited in the above invention, preferably theirradiating means has a plurality of irradiating units for irradiatingthe interface portion from mutually different angles (see claim 13).

Although not particularly limited in the above invention, preferably theplurality of irradiating units include: a first irradiating unit forirradiating the interface portion from a first angle and a secondirradiating unit for irradiating the interface portion from a secondangle different from the first angle, and the failure detecting meansspecifies, as the appearance failure area of the interface portion, anarea having a first contrasting density difference from a background ina first real image information picked up by the imaging means when thefirst irradiating unit irradiates the interface portion and having asecond contrasting density difference from a background in a second realimage information picked up by the imaging means when the secondirradiating unit irradiates the interface portion (see claim 14).

Although not particularly limited in the above invention, preferably theclassifying section classifies the appearance failure area into any oneof the failure categories on the basis of at least one of contrastingdensity, shape, or position of the appearance failure area in the firstreal image information and at least one of contrasting density, shape,or position of the appearance failure area in the second real imageinformation (see claim 15).

Although not particularly limited in the above invention, preferably theobtaining means includes a three-dimensional measurement apparatus forthree-dimensionally obtaining the appearance information of theinterface portion (see claim 16).

Although not particularly limited in the above invention, preferably theabnormality detecting apparatus further comprises a starting means forstarting the obtaining means at a predetermined timing so that theobtaining means obtains the appearance information of the interfaceportion, or for making the failure detecting means detect the appearancefailure of the interface portion at a predetermined timing (see claim17).

Although not particularly limited in the above invention, preferably theabnormality detecting apparatus further comprises a counting means forcounting a number of contacts of the device under test with the contactportion or counting an occurring number of a predetermined type offailure which occurs in the device under test, and the starting meansstarts the obtaining means or makes the failure detecting means detectthe appearance failure of the interface portion when the counting meanscounts up to a predetermined number (see claim 18).

Although not particularly limited in the above invention, preferably theabnormality detecting apparatus further comprises a timing means formeasuring an elapsed time after starting the test of the device undertest, and the starting means starts the obtaining means or makes thefailure detecting means detect the appearance failure of the interfaceportion when the timing means completes to measure a predetermined timeduration (see claim 19).

(2) To achieve the above object, according to a second aspect of thepresent invention, there is provided an electronic device testingapparatus for testing a device under test, comprising: a contact arm forpressing the device under test onto a contact portion of a test head;and the above abnormality detecting apparatus (see claim 20).

(3) To achieve the above object, according to a third aspect of thepresent invention, there is provided an electronic device testing systemcomprising: a plurality of electronic device testing apparatuses eachhaving a contact arm for pressing a device under test onto a contactportion of a test head and an abnormality detecting apparatus fordetecting an abnormality of an interface portion with the device undertest, the interface portion being provided with the contact arm; and ahost computer connected with the electronic device testing apparatusesvia a communication means, wherein the abnormality detecting apparatuscomprises: an obtaining means for obtaining an appearance information ofthe interface portion of the contact arm; a failure detecting means fordetecting an appearance failure of the interface portion on the basis ofthe appearance information obtained by the obtaining means; and adetermining means for determining whether the abnormality occurs at theinterface portion on the basis of a detection result by the failuredetecting means, the determining means has: a classifying section forclassifying the appearance failure detected by the failure detectingmeans into a plurality of failure categories on the basis ofpredetermined criteria; a counting section for counting a number offailures in each of the failure categories and generating an actualcount number for each category; and a comparing section for comparingthe actual count number generated by the counting section with areference count number for each category with respect to each of thefailure categories. and determining whether the abnormality occurs atthe interface portion on the basis of the comparison result, thereference count number being preliminarily set as a reference number offailures in each of the failure categories, and each of the electronicdevice testing apparatuses informs of the actual count number generatedby the counting section to the host computer via the communication meansin response to a request from the host computer (see claim 21).

Although not particularly limited in the above invention, preferably thecomparing section of the abnormality detecting apparatus determines thatthe abnormality occurs at the interface portion when the actual countnumber is larger than the reference count number with respect to atleast one of the failure categories (see claim 22).

Although not particularly limited in the above invention, preferably theabnormality detecting apparatus further comprises an alarming means forinforming that the interface portion is abnormal or informing of afailure category which is a cause for an occurrence of the abnormalityat the interface portion when the comparing section determines that theabnormality occurs at the interface portion (see claim 23).

(4) To achieve the above object, according to a fourth aspect of thepresent invention, there is provided an abnormality detecting method fordetecting an abnormality of an interface portion with a device undertest, the interface portion being provided with a contact arm forpressing the device under test onto a contact portion of a test head ata time of testing the device under test, the abnormality detectingmethod comprising: an obtaining step of obtaining an appearanceinformation of the interface portion of the contact arm; a failuredetecting step of detecting an appearance failure of the interfaceportion on the basis of the appearance information obtained in theobtaining step; and a determining step of determining whether theabnormality occurs at the interface portion on the basis of a detectionresult in the failure detecting step (see claim 24).

Although not particularly limited in the above invention, preferably theinterface portion includes a thin-plate-shaped member or athin-film-shaped member provided on a front end of the contact arm, or aliquid applied on the front end of the contact arm (see claim 25).

Although not particularly limited in the above invention, preferably thedetermining step includes: a classifying step of classifying theappearance failure detected in the failure detecting step into aplurality of failure categories on the basis of predetermined criteria;a counting step of counting a number of failures in each of the failurecategories and generating an actual count number for each category; anda comparing step of comparing the actual count number generated in thecounting step with a reference count number for each category withrespect to each of the failure categories, and determining whether theabnormality occurs at the interface portion on the basis of thecomparison result, the reference count number being preliminarily set asa reference number of failures in each of the failure categories (seeclaim 26).

Although not particularly limited in the above invention, preferably, inthe comparing step, it is determined that the abnormality occurs at theinterface portion when the actual count number is larger than thereference count number with respect to at least one of the failurecategories (see claim 27).

Although not particularly limited in the above invention, preferably theabnormality detecting method further comprises an alarming step ofinforming that the interface portion is abnormal or informing of afailure category which is a cause for an occurrence of the abnormalityat the interface portion when it is determined that the abnormalityoccurs at the interface portion in the comparing step (see claim 28).

Although not particularly limited in the above invention, preferably, inthe obtaining step, a real image information of the interface portion isobtained by picking up an image of the interface portion (see claim 29).

Although not particularly limited in the above invention, preferably, inthe failure detecting step, an area having a predetermined contrastingdensity difference from a background in the real image informationpicked up in the obtaining step is specified as the appearance failurearea of the interface portion (see claim 30).

Although not particularly limited in the above invention, preferably, inthe classifying step, the appearance failure area is classified into anyone of the failure categories on the basis of at least one ofcontrasting density, shape, or position of the appearance failure areaspecified in the failure detecting step (see claim 31).

Although not particularly limited in the above invention, preferably theabnormality detecting method further comprises a memorizing step ofmemorizing, as a reference image information of the interface portion,an image information of the interface portion preliminarily picked up,and, in the failure detecting step, a differential image information isgenerated by performing a differential processing between the real imageinformation picked up in the obtaining step and the reference imageinformation memorized in the memorizing step, and an area having apredetermined contrasting density difference from a background in thedifferential image information is specified as the appearance failurearea of the interface portion (see claim 32).

Although not particularly limited in the above invention, preferably, inthe classifying step, the appearance failure area is classified into anyone of the failure categories on the basis of at least one ofcontrasting density, shape, or position of the appearance failure areain the differential image information (see claim 33).

Although not particularly limited in the above invention, preferably, inthe obtaining step, a first real image information is obtained bypicking up an image of the interface portion while irradiating theinterface portion from a first angle and a second real image informationis obtained by picking up an image of the interface portion whileirradiating the interface portion from a second angle different from thefirst angle, and in the failure detecting step, an area having a firstcontrasting density difference from a background in the first real imageinformation and having a second contrasting density difference from abackground in the second real image information is specified as theappearance failure area of the interface portion (see claim 34).

Although not particularly limited in the above invention, preferably, inthe classifying step, the appearance failure area is classified into anyone of the failure categories on the basis of at least one ofcontrasting density, shape, or position of the appearance failure areain the first real image information and at least one of contrastingdensity, shape, or position of the appearance failure area in the secondreal image information (see claim 35).

Although not particularly limited in the above invention, preferably, inthe obtaining step, the interface portion is irradiated with visuallight ray or ultraviolet ray, and visual light ray or ultraviolet rayreflected from the interface portion is received thereby the real imageinformation of the interface portion is obtained (see claim 36).

Although not particularly limited in the above invention, preferably, inthe obtaining step, the appearance information of the interface portionis three-dimensionally obtained (see claim 37).

Although not particularly limited in the above invention, preferably theobtaining step or the failure detecting step is executed when a numberof contacts of the device under test with the contact portion is equalto or larger than a predetermined number, an occurring number of apredetermined type of failure which occurs in the device under test isequal to or larger than a predetermined number, or a predetermined timeduration is elapsed after starting the test of the device under test(see claim 38).

ADVANTAGEOUS EFFECT OF THE INVENTION

In the present invention, an appearance failure of the interface portionof the contact arm is detected, and it is determined whether anabnormality occurs at the interface portion or not on the basis of thedetection result thereof. Therefore, it is possible to maintain a goodheat conductivity between the contact arm and the device under test.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view illustrating an electronic device testingapparatus according to an embodiment of the present invention.

FIG. 2 is a cross sectional view along the line II-II in FIG. 1.

FIG. 3 is a schematic cross sectional view of a contact arm according tothe embodiment of the present invention.

FIG. 4 is a block diagram illustrating an abnormality detectingapparatus according to the embodiment of the present invention.

FIG. 5 is a cross sectional view along the line V-V in FIG. 1.

FIG. 6 is a schematic cross sectional view illustrating a irradiatingdevice according to the embodiment of the present invention.

FIG. 7 is a plan view illustrating areas of a TIM according to theembodiment of the present invention.

FIG. 8 is a block diagram illustrating an electronic device testingsystem according to the embodiment of the present invention.

FIG. 9 is a flowchart illustrating an abnormality detecting method for aTIM according to the embodiment of the present invention.

FIG. 10A is a view illustrating an example of image data of a TIMwithout appearance failures in the embodiment according to the presentinvention.

FIG. 10B is a view illustrating an example of image data of a TIM withappearance failures in the embodiment according to the presentinvention.

FIG. 10C is a view illustrating an example of differential image data ofa TIM generated in an another embodiment according to the presentinvention.

[Reference Signs List] 150; moving apparatus 160; contact arm 161;pusher 167; TIM 167a; appearance failures 200; abnormality detectingapparatus 210; imaging device 220; irradiating device 230; startingdevice 240; image processor device 241; failure detecting section 250;memory device 260; determining device 261; classifying section 262;counting section 263; comparing section 270; alarming device

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments according to the present invention will bedescribed referring to the drawings.

FIG. 1 is a plan view illustrating an electronic device testingapparatus according to an embodiment of the present invention, FIG. 2 isa cross sectional view along the line II-II in FIG. 1, FIG. 3 is aschematic cross sectional view illustrating a contact arm according tothe embodiment of the present invention, FIG. 4 is a block diagramillustrating an abnormality detecting apparatus according to theembodiment of the present invention, FIG. 5 is a cross sectional viewalong the line V-V in FIG. 1, FIG. 6 is a schematic cross sectional viewillustrating a irradiating device according to the embodiment of thepresent invention, FIG. 7 is a plan view illustrating areas of a TIMaccording to the embodiment of the present invention, and FIG. 8 is ablock diagram illustrating an electronic device testing system accordingto the embodiment of the present invention.

As shown in FIG. 1 and FIG. 2, the electronic device testing apparatusaccording to the present embodiment comprises a handler 100, a test head10, and a tester 20, and the test head 10 and the tester 20 areconnected with each other via a cable 30. The handler 100 presses ICdevices onto sockets 11 of the test head 10 and the tester 20 executes atest of each IC device via the test head 10 and the cable 30, thereafterthe handler 100 classifies the IC device completed to be tested inaccordance with the test result. Note that, an IC device is indicated bycharacter “IC” in the drawings.

The handler 100 comprises some kinds of trays 111 to 113, a transporter120, a heat plate 130, buffers 140, and a moving apparatus 150. Inaddition, the handler 100 has an apparatus board 101 formed with anopening 102. As shown in FIG. 2, the sockets 11 of the test head 10approach through the opening 102 into the handler 100, thereby it ispossible to press IC devices onto the sockets 11.

The transporter 120 comprises: rails 121 installed along the X axisdirection on the apparatus board 101; a movable rail 122 established tobe movable along the X axis direction on the rails 121; a movable head123 supported by the movable rail 122 so as to be movable along the Yaxis direction; and two suction heads 124 attached to the lower part ofthe movable head 123. Each of suction heads 124 is capable of beingmovable along the Z axis direction (that is, up-and-down direction) bymeans of a Z axis direction actuator not particularly shown in thedrawings.

The transporter 120 has an operation area covering a supplying tray 112on which IC devices to be tested are stored, classified trays 113 onwhich IC devices completed to be tested are stored after beingclassified in accordance with the test results, an empty tray 111without IC devices stored thereon, the heat plate 130, and two bufferunits 140.

The transporter 120 is capable of transporting at the same time two ICdevices to be tested from the supplying tray 112 to the heat plate 130or from the heat plate 130 to the buffer unit 140 or transporting alsoat the same time two IC devices completed to be tested from the bufferunit 140 to the categorized tray 113. Note that, in the presentinvention, the number of IC devices to be transported at the same timeby the transporter 120 may be arbitrarily set. For example, four, eight,16, or 32 devices may be transported at the same time.

The heat plate 130 is, for example, a metal plate formed with aplurality of concave portions 131 thereon, and an IC device is to bedropped into each of the concave portions 131. Although not particularlyshown in the drawings, a heater is provided below the heat plate 130 inorder to heat IC devices via the heat plate 130. The transporter 120transports each IC device from the supplying tray 112 to each concaveportion 131 of the heat plate 130. After IC devices are heated to apredetermined temperature by the heat plate 130, the IC device istransported to either one (for example, upper side one in FIG. 1) of thebuffer units 140 by the transporter 120.

The two buffer units 140 are capable of reciprocally moving between theoperation area of the transporter 120 and an operation area of themoving apparatus 150 by means of rails 141 provided on the apparatusboard 101 and actuators not shown. The buffer unit 140 located at upperside in FIG. 1 performs an operation to move IC devices transported fromthe heat plate 130 by the transporter 120 to the operation area of themoving apparatus 150. On the other hand, the buffer unit 140 located atlower side in FIG. 1 performs an operation to move out IC devicescompleted to be tested by the test head 10 to the operation area of thetransporter apparatus 120.

The moving apparatus 150 comprises: rails 151 installed along the X axisdirection on the apparatus board 101; a movable rail 152 established tobe movable along the X axis direction on the rails 151; a movable head153 supported by the movable rail 152 so as to be movable along the Yaxis direction; and two contact arms 160 attached to the lower part ofthe movable head 153 and capable of holding IC devices by suction. Eachcontact arm 160 is movable along the Z axis direction (that is,up-and-down direction) by means of a Z axis direction actuator notparticularly shown in the drawings.

The moving apparatus 150 has the operation area covering the two bufferunits 140 and the test head 10. Two IC devices is held by suction fromthe buffer unit 140 located at upper side in FIG. 1 at the same time,and the IC devices are moved to the sockets 11 of the test head 10 andare pressed onto the sockets 11 at the same time, the IC devices aretransported to the buffer unit 140 located at lower side in the figure.Note that, in the present invention, the number of the contact arms 160attached to the moving apparatus 150 may be arbitrarily set depending onthe number of the sockets 11 of the test head 10.

As shown in FIG. 3, each of the contact arms 160 has a pusher 161 on thelower portion thereof in order to press an IC device onto the socket 11at the time of testing. A suction pad 162 for holding the IC device bysuction is provided approximately at the center of the bottom surface ofthe pusher 161. The suction pad 162 is connected with a negativepressure source not depicted in the figure via a pipe 163 providedinside the contact arm 160.

A heater 164 is provided inside the pusher 161 and is configured with,for example, an electrical heater or the like so as to be able to heatthe pusher 161. Also a water jacket 165 which forms a cooler is providedinside the pusher 161. The water jacket 165 is connected with a chillernot depicted in the figure and the pusher 161 is cooled by circulating arefrigerant through the water jacket 165.

Furthermore, a temperature sensor 166 which measures a temperature ofthe pusher 161 is provided inside the pusher 161. By controllingoperations of the heater 164 and the cooler on the basis of themeasuring result of the temperature sensor 166, it is possible tomaintain the temperature of the IC device at a predeterminedtemperature.

In addition, in the present embodiment, a TIM (Thermal InterfaceMaterial) 167 is attached to the bottom end surface (front end surface)of the pusher 161. The TIM 167 is composed of a material with highthermal conductivity and softness for deformability. The TIM 167 deformsbetween the bottom end surface of the pusher 161 and the upper surfaceof the IC device when the contact arm 160 presses the IC device. Whilevoids are formed between the bottom end surface of the pusher 161 andthe upper surface of the IC device due to microscopic irregularitieswith both the surfaces, the TIM 167 deforms so as to fill the voids, andthe pusher 161 and the IC device are close contact with each other,thereby the thermal resistance between the pusher 161 and the IC devicedecreases.

As specific examples of the TIM 167, for example, solid types such asmetal foils formed of aluminum, copper, and the like and carbon graphitesheets, gel types like gel states, hybrid types with gel typesinterleaved between solid types, and liquid types such as glycerine andwater may be mentioned.

At the time of testing an IC device, as shown in FIG. 3, the contact arm160 presses the IC device onto the socket 11 of the test head 10 in thestate where the suction pad 162 holds the IC device by suction, andcontacts each terminal HB of the IC device with each contact pin 12 ofthe socket 11. In this state, the tester 20 inputs and outputs a testingsignal with respect to the IC device, thereby executing a test of the ICdevice.

Moreover, in the present embodiment, an abnormality detecting apparatus200 is provided in the operation area of the moving apparatus 150 inorder to detect an abnormality occurring at the TIM 167 attached to thecontact arm 160.

As shown in FIG. 4, the abnormality detecting apparatus 200 comprises animaging device 210, a irradiating device 220, a starting device 230, animage processor device 240, a memory device 250, a determining device260, and an alarming device 270.

The imaging device 210 has, for example, a CCD sensor or a CMOS sensor.As shown in FIG. 5, the imaging device 210 is arranged in a recessedarea 103 with a posture where the optical axis OL is directed upward andthe recessed area 103 is formed on the apparatus board 101. Therefore,it is possible that the imaging device 210 images the TIM 167 attachedto the contact arm 160 from immediately below. As shown in FIG. 4, theimaging device 210 is connected with the image processor device 240 soas to be able to transmit the image data on which the TIM 167 iscaptured. Note that, for example, a three-dimensional measurementapparatus using a semiconductor laser is also available for the imagingdevice 210.

As shown to FIG. 4 to FIG. 6, the irradiating device 220 has twoirradiating units 221 and 222. The first irradiating unit 221 isconfigured with, for example, LEDs arranged in a circular pattern,thereby the center of the bottom surface of the TIM 167 is irradiatedwith visual light rays at a first angle α. While the second irradiatingunit 222 is also configured with, for example, LEDs arranged in acircular pattern, the second irradiating unit 222 is provided on thelower side than the first irradiating unit 221, thereby the center ofthe bottom surface of the TIM 167 is irradiated with visual light raysat a second angle β.

Herein, the first angle α is, for example, approximately 0 degree to 10degree of a low angle with respect to the TIM 167. On the contrary, thesecond angle β is, for example, approximately 30 degree to 60 degree ofa medium angle with respect to the TIM 167. Using the first irradiatingunit 221 of low angle allows to easily detect, for example, lineal scarsand microscopic foreign particles. On the other hand, using the secondirradiating unit 222 of medium angle allows to easily detect, forexample, defects having relatively large surface areas and the like.Note that, in the present invention, the number of the irradiating unitsin the irradiating device 220 is not limited to two, and the irradiatingdevice may have three or more of the irradiating units.

A color of the irradiating light from the irradiating device 220 may beset depending on the color of the TIM 167, and white or blue may beillustrated by example. In the present invention, the irradiating lightfrom the irradiating device 220 is not particularly limited to visiblelight rays and may be, for example, ultraviolet rays. In the case ofirradiating the surface of the TIM 167 with ultraviolet rays, it ispossible to detect microscopic changes occurred on the surface of theTIM 167 by comparison with the case of irradiating with visual lightrays. When the irradiating device 220 irradiates with visual light rays,a camera capable of receiving visual light rays is used as the imagingdevice 210, whereas when the irradiating device 220 irradiates withultraviolet rays, a camera capable of receiving ultraviolet rays is usedas the imaging device 210.

The starting device 230 has a counter 231 for countering a number ofcontacting between IC devices and the socket 11 (the number being alsosimply referred to as “contact number”, hereinafter) on the basis of thesignal from the tester 20. The starting device 230 starts the imagingdevice 210 and the irradiating device 220 at the time when the counter231 counts up to a predetermined number.

Note that, the counter 231 may count an occurrence number of IC devicesspecified with certain testing results on the basis of the signal fromthe tester 20, and in this case the starting device 230 starts theimaging device 210 and the irradiating device 220 on the basis of withthe count result. As examples of the certain testing results (failuremodes), a failure and the like regarding the temperature controldetected by using a thermal diode provided in the IC device may bementioned.

In addition, instead of the counter 231, a timer may be provided in thestarting device 230 and accumulate an elapsed time after starting totest IC devices. In this case, the starting device 230 starts theimaging device 210 and the irradiating device 220 when the timercompletes to measure a predetermined time duration.

Moreover, the starting device 230 may automatically start the imagingdevice 210 and the irradiating device 220 at the time a testing lot ofIC devices is started or finished. Alternatively, the starter device 230may automatically start the imaging device 210 and the irradiatingdevice 220 at the time an abnormality of the handler 100 is recovered.

The image processor device 240 is configured with an image processor, aROM, a RAM, and the like not particularly shown in figures, andfunctionally has a failure detecting section 241. The failure detectingsection 241 specifies an appearance failure area of the TIM 167 byprocessing an image data of the TIM 167 transmitted from the imagingdevice 210 and transmits the specified failure date to the determiningdevice 260. The specified failure data includes a contrasting densitydifference, a shape, a position, and the like regarding the appearancefailure area.

Herein, the contrasting density difference means a contrasting densitydifference between the appearance failure area and the periphery thereofin the image data. Further, as examples of the shape, a surface area ofthe appearance failure area, a boundary length of the appearance failurearea, a degree of circularity of the appearance failure area, a maximumlength of the appearance failure area, a length in the directionorthogonal to the maximum length in the appearance failure area, and awidth and a height of a virtual rectangle circumscribing the appearancefailure area, and the like may be mentioned. Furthermore, the positionmeans a coordinate value or the like of the appearance failure area inthe image data.

The determining device 260 is configured with a computer having an MPU,a RAM, a ROM, and the like, and functionally has a classifying section261, a counting section 262, and a comparing section 263.

The classifying section 261 classifies the appearance failure area ofthe TIM specified by the failure detecting section 241 into a pluralityof failure categories on the basis of predetermined criteria. Asspecific examples of the predetermined criteria for classifying theappearance failure, a region in the TIM 167 to which the appearancefailure belongs, a type of the appearance failure of the TIM 167, andthe like may be mentioned.

As shown in FIG. 7, as examples of the region in the TIM 167 to whichthe appearance failure belongs, areas AR₁ to AR₉ to which the appearancefailure belongs when the surface of the TIM 167 is divided into nineareas may be mentioned.

In addition, as examples of types of the appearance failures at the TIM167, for example, scars, defects (cracks, holes, and peripheraldefects), attached foreign particles (attachment of dusts, trashes, andsolder balls), and the like may be mentioned.

Thus, the number of failure categories becomes 63 (˜9×7) by dividing thelocations at the TIM 167 into nine areas AR₁ to AR₉ and classifyingappearance failures occurred respectively in the areas AR₁ to AR₉ intothe above seven types of the appearance failures.

The counting section 262 counts a number of appearance failures occurredin each of the above failure categories and generates an actual countnumber P_(N,m) for each category. Note that, the subscript N of theactual count number P_(N,m) represents a number of contacts at the timewhen the failure detecting section 241 detects an appearance failure.Moreover, the subscript m of the actual count number P_(N,m) representsa numeral of the failure category, that is, m=(1 to 63) in the aboveexample.

For example, in the above example, m=(1 to 9) indicate respectively theoccurring numbers of the “scars” in the areas AR₁ to AR₉, m=(10 to 18)indicate respectively the occurring numbers of the “cracks” in the areasAR₁ to AR₉, . . . , and m=(55 to 63) indicate respectively the occurringnumbers of the “attachment of solder balls” in the areas AR₁ to AR₉.

Firstly, the comparing section 263 reads a reference count numberQ_(N,m) for each category from the memory device 250 and compares theactual count number P_(N,m) generated by the counting section 262 withthe reference count number Q_(N,m) with respect to each failurecategory. Then, the comparing section 263 determines that an abnormalityoccurs at the TIM 167 when the actual count number P_(N,m) is largerthan the reference count number Q_(N,m) in any one of the failurecategories (P_(N,m)>Q_(N,m)) and transmits a command signal to thealarming device 270.

Herein, for example, in the case that the pusher 161 of the contact arm160 has a lower end surface with insufficient flatness, the “scars”occurs considerably and partially at the TIM 167. Moreover, in the casethat the contact arm 160 is inclined, the TIM 167 is worn unevenly andthe “peripheral defects” occurs. Furthermore, in the case that ICdevices have burrs or the handler 100 is used in a dusty environment,considerable “foreign particles” are attached to the TIM 167. In thepresent embodiment, such abnormalities of the TIM 167 are detected bycomparing the actual count number P_(N,m) with the reference countnumber Q_(N,m) with respect to each failure category.

The reference count number Q_(N,m) stored in the memory device 250 is adata which is obtained by classifying appearance failures which occur ata TIM 167 over time in situation where the TIM 167 is used in an averageenvironment into the above failure categories, and preliminarilycounting a number of the appearance failure areas with respect to eachfailure category. The reference count number Q_(N,m) is stored in thememory device 250 for each certain contact number (for example, each 100times of contacts).

The alarming device 270 alarms an operator via for example a speaker, anoperation screen of the handler 100, and the like in response to thecommand signal from the determining device 260 and informs that the TIM167 is in abnormality. Note that, the alarming device 270 may inform ofthe failure category which is a cause for an occurrence of theabnormality at the TIM 167. The operator can immediately anticipate acause of the abnormality occurrence by being informed of the failurecategory as the cause.

As shown in FIG. 8, in the case that a plurality of electronic devicetesting apparatuses each configured with the handler 100, the test head10, and the tester 20 are connected with a host computer 40 via acommunication means such as an in-plant LAN, the abnormality detectingapparatus 200 may transmit the actual count number P_(N,m) generated bythe counter section 262 of the determining device 260 to the hostcomputer 40.

FIG. 9 is a flowchart illustrating an abnormality detecting method for aTIM according to the embodiment of the present invention, FIG. 10A is aview illustrating an example of image data of a TIM without appearancefailures in the embodiment according to the present invention, FIG. 10Bis a view illustrating an example of image data of a TIM with appearancefailures in the embodiment according to the present invention, and FIG.10C is a view illustrating an example of differential image datagenerated in an another embodiment according to the present invention.

Hereinafter, the abnormality detecting method for a TIM according to theembodiment of the present invention will be described referring to FIG.9.

At first, as shown in FIG. 9, after the contact arm 160 of the handler100 presses IC devices onto the sockets 11 and the tester 20 executestesting of the IC devices (step S100), the counter 231 of the startingdevice 230 adds 1 to the contact number n (step S110). The startingdevice 230 compares the counting result n by the counter 231 with apredetermined number N (for example 100 times), and if it is determinedthat the counting result n is smaller than the predetermined number N,the handler 100 continues to test the IC devices (NO in step S120).

On the contrary, if the counting result n is the predetermined number Nor more (YES in step S120), the contact arm 160 moves to the abnormalitydetecting apparatus 200 (step S130), and the starting device 230 startsthe imaging device 210 and the irradiating device 220 (step S140).Particularly in step S130, the contact arm 160 moves downward to thevicinity of the irradiating device 220, thereby it is minimallysuppressed that external light lights the TIM 167.

After the starting device 230 starts the imaging device 210 and theirradiating device 220, the irradiating device 220 irradiates the TIM167, and the imaging device 210 picks up an image of the TIM 167 (stepS150).

The image data of the TIM 167 obtained by the imaging device 210 istransmitted to the image processor device 240. The failure detectingsection 241 of the image processor device 240 specifies an appearancefailure area at the TIM 167 by subjecting the image data to an imageprocessing such as a threshold processing and a blob processing (stepS160).

Specifically, the appearance failure is specified as follows. While theTIM 167 without appearance failures provides image data having an evenbrightness as shown in FIG. 10A, the TIM 167 with appearance failures167 a provides contrasts (contrasting density differences) at thelocations of the appearance failures 167 a as shown in FIG. 10B.Consequently, in the present embodiment, the threshold processing isused to specify, as appearance failures, bright areas with certainhigher brightness or more relatively to the background in TIM 167 ordark areas with certain lower brightness or less relatively to thebackground in TIM 167.

Note that, appearance failure areas of the TIM 167 may be specified asfollows. Firstly, the image data of a TIM 167 without appearancefailures as shown in FIG. 10A is preliminarily stored in the memorydevice 250 as reference image data. Then, the failure detecting section241 reads the reference image data from the memory device 250, andgenerates a differential image data (refer to FIG. 10C) between the realimage data (refer to FIG. 10B) obtained by the imaging device 210 andthe reference image data. In this differential image data, bright areaswith certain higher brightness or more relatively to the background ordark areas with certain lower brightness or less relatively to thebackground are specified as the appearance failures 167 a.

Particularly in the case of adopting a three-dimensional measurementapparatus, it is possible to directly obtain irregularity on the surfaceof the TIM 167 as a height data, and portions in which the height datachanges are specified as appearance failure areas.

After specifying the appearance failure areas at the TIM 167, thefailure detecting section 241 transmits a specified failure data to thedetermining device 160. The specified failure data includes acontrasting density difference, a shape, and a position with respect toeach failure area.

The classifying section 261 of the determining device 260 classifies theappearance failure areas specified by the failure detecting section 241into failure categories (step S170). More specifically, the appearancefailure areas are firstly classified into the areas AR₁ to AR₉, andthen, in each of the areas AR₁ to AR₉, the appearance failure areas areclassified into types such as “scars” and “cracks” on the basis of thecontrasting density differences and shapes of the appearance failureareas. As a result in the above example, the appearance failuresoccurred at the TIM 167 are classified into 63 types of failurecategories.

For example, if the length in the direction orthogonal to the maximumlength of an appearance failure area is shorter than the maximum length(i.e. the appearance failure area is elongated) and the appearancefailure area is brighter than the background, the appearance failure isclassified into “scars”.

On the other hand, if an appearance failure is elongated and bright areaand dark area pair up, the appearance failure area is classified into“cracks”.

Moreover, if an appearance failure area is dark under the firstirradiating unit 221 irradiating the TIM 167 (having a first contrastingdensity difference from the background), is bright under the secondirradiating unit 222 (having a second contrasting density differencefrom the background), and has a relatively small surface area, theappearance failure area is classified into “attachment of dusts”.

Furthermore, if an appearance failure area is relatively bright comparedto the peripheral area thereof and the degree of circularity (=(boundarylength)²/(surface area)) is approximately equal to 4π, the appearancefailure area is classified into “attachment of solder balls”.

In addition, portions which are other than the above and have relativelylarge surface areas are specified as “holes”, “peripheral defects”, and“attachment of trashes”. Further, “holes” and “peripheral defects” aredistinguished according to the positional relationship between the TIM167 and the appearance failure areas, and “holes” and “attachment oftrashes” are distinguished according to the difference in brightness.Note that, the types of appearance failures and classifying methodthereof described herein are merely examples, and the present inventionis not particularly limited to the examples.

Then, the counting section 262 of the determining device 260 counts thenumber of appearance failure areas in each failure category andgenerates the actual count number P_(N,m) for each category (step S180).

Next, the comparing section 263 of the determining device 260 reads thereference count number Q_(N,m) for each category from the memory device250 (step S190), and compares the actual count number P_(N,m) generatedby the counting section 262 with the reference count number Q_(N,m) withrespect to each failure category (step S190).

In the comparison of step S190, if it is determined that the actualcount number P_(N,m) is the reference count number Q_(N,m) or less inany failure category (NO in step S200), the comparing section 263determines that an abnormality is absent at the TIM 167. In this case,after adding, for example, 100 to N (step S200), the handler 100continues to perform the test of the IC device. According to step S200,the next abnormality detecting of the TIM 167 is automatically executedafter further counting the contact number of 100 times.

On the contrary, in the comparison of step S190, if it is determinedthat the actual count number P_(N,m) is larger than the reference countnumber Q_(N,m) (P_(N,m)>Q_(N,m)) in any one of the failure categories,the comparing section 263 transmits the command signal to the alarmingdevice 270 (YES in step S200). Note that, the comparing section 263 maytransmit the command signal to the alarming device 270 only when it isdetermined that the actual count number P_(N,m) is larger than thereference count number Q_(N,m) (P_(N,m)>Q_(N,m)) in a plurality of thefailure categories.

The alarming device 270 informs, for example, an operator that anabnormality occurs at the TIM 167 in accordance with the command signalfrom the comparing section 263 (step S220).

As described above, in the present embodiment, appearance failures ofthe TIM 167 are detected, and it is determined whether an abnormalityoccurs at the TIM 167 on the basis of the detecting result. Therefore,it is possible to maintain a good heat conductivity between the pusher161 of the contact arm 160 and IC devices.

Note that, the embodiments explained above were described to facilitatethe understanding of the present invention, but were not described tolimit the present invention. Therefore, the elements disclosed in theembodiments include all design equivalents falling under the technicalscope of the present invention.

For example, although the above embodiments are described as such thatthe contact arm 160 is provided with both the heater 164 and the cooler165, the present invention is not particularly limited to this. Forexample, the present invention may be applied to a contact arm providedmerely with a heater.

Moreover, although the above embodiments are described as such thatfailures are classified into failure categories in accordance withcontrasting density, shape, and position, the present invention is notparticularly limited to this. For example, failures may be classifiedinto failure categories in accordance merely with only position or inaccordance with contrasting density and position.

Furthermore, although the above embodiments are described as such thatthe abnormality of the TIM 167 attached to the front end of the contactarm 160 is detected by using the abnormality detecting apparatus 200,the present invention is not particularly limited to this. For example,in the case of a type of contact arm not to be attached with the TIM167, an abnormality of the front end surface of the pusher provided withthe contact arm may be detected by using the abnormality detectingapparatus according to the present invention.

Still furthermore, at the time of peeling off the TIM of the gel type orthe liquid type from the pusher 161, the abnormality detecting apparatusaccording to the present invention may be used for detecting the wipingremain of the TIM (contamination or residue due to the TIM) as anabnormality of the bottom end surface of the pusher 161.

In addition, although the above embodiments are described as such thatthe starting device 230 starts the imaging device 210 and theirradiating device 220 at a predetermined timing, the present inventionis not particularly limited to this. For example, while the imagingdevice 210 and the irradiating device 220 are continuously operating,the starting device 230 may make the failure detecting section 241detect appearance failures of the TIM 167 at a predetermined timing.

The invention claimed is:
 1. An abnormality detecting apparatusconfigured to detect an abnormality of an interface portion of a contactarm of an electric device testing apparatus that tests a device undertest the interface portion contacting the device under test when testingthe device under test, the abnormality detecting apparatus comprising:an obtaining device configured to obtain appearance information of theinterface portion of the contact arm, when the interface portion is outof contact with the device under test; a failure detector configured todetect an appearance failure of the interface portion of the contact armon the basis of the appearance information obtained by the obtainingdevice; and a determining device configured to determine whether theabnormality occurs at the interface portion on the basis of a detectionresult by the failure detector.
 2. The abnormality detecting apparatusas set forth in claim 1, wherein the interface portion includes athin-plate-shaped member or a thin-film-shaped member provided on afront end of the contact arm, or a liquid applied on the front end ofthe contact arm.
 3. The abnormality detecting apparatus as set forth inclaim 1, wherein the determining device has: a classifier configured toclassify the appearance failure detected by the failure detector into aplurality of failure categories on the basis of predetermined criteria;a counter configured to count a number of failures in each of thefailure categories, and to generate an actual count number for eachcategory; and a comparator configured to compare the actual count numberwith a reference count number with respect to each of the failurecategories, and to determine whether the abnormality occurs at theinterface portion on the basis of the comparison result, the referencecount number being set in advance as a reference number of failures ineach of the failure categories.
 4. The abnormality detecting apparatusas set forth in claim 3, wherein the comparator determines that theabnormality occurs at the interface portion when the actual count numberis larger than the reference count number with respect to at least oneof the failure categories.
 5. The abnormality detecting apparatus as setforth in claim 4, further comprising an alarm configured to inform thatthe interface portion is abnormal, or to inform of a failure categorywhich is a cause for an occurrence of the abnormality at the interfaceportion of the contact arm when the comparator determines that theabnormality occurs at the interface portion.
 6. The abnormalitydetecting apparatus as set forth in claim 1, wherein the obtainingdevice includes an imaging device configured to pick up an image of theinterface portion of the contact arm.
 7. The abnormality detectingapparatus as set forth in claim 6, wherein the failure detectorspecifies, as an appearance failure area of the interface portion of thecontact arm, an area having a predetermined contrast density differencefrom a background in the image of the interface portion picked up by theimaging device.
 8. The abnormality detecting apparatus as set forth inclaim 7, further comprising classify the appearance failure area intoone of a plurality of failure categories, on the basis of at least oneof contrasting density, shape, or position of the appearance failurearea specified by the failure detector.
 9. The abnormality detectingapparatus as set forth in claim 6, further comprising a memory deviceconfigured to memorize reference image information of the interfaceportion which is picked up in advance by the imaging device as areference, wherein the failure detector generates a differential imageinformation by performing differential processing between the image ofthe interface portion of the contact arm picked up by the imaging deviceand the reference image information memorized in the memory device andspecifies, as an appearance failure area of the interface portion, anarea having a predetermined contrast density difference from abackground in the differential image information.
 10. The abnormalitydetecting apparatus as set forth in claim 9, further comprising aclassifier configured to classify the appearance failure area into oneof failure categories on the basis of at least one of contrastingdensity, shape, or position of the appearance failure area in thedifferential image information.
 11. The abnormality detecting apparatusas set forth in claim 6, further comprising an irradiating deviceconfigured to irradiate the interface portion.
 12. The abnormalitydetecting apparatus as set forth in claim 11, wherein the irradiatingdevice irradiates the interface portion with a visible light ray or anultraviolet ray, and the imaging device receives the visible light rayor the ultraviolet ray.
 13. The abnormality detecting apparatus as setforth in claim 11, wherein the irradiating device has a plurality ofirradiators configured to irradiate the interface portion from mutuallydifferent angles.
 14. The abnormality detecting apparatus as set forthin claim 13, wherein the plurality of irradiators include: a firstirradiator configured to irradiate the interface portion from a firstangle; and a second irradiator configured to irradiate the interfaceportion from a second angle different from the first angle, and thefailure detector specifies, as an appearance failure area of theinterface portion, an area having a first contrast density differencefrom a background in first real image information picked up by theimaging device when the first irradiator irradiates the interfaceportion and having a second contrast density difference from abackground in second real image information picked up by the imagingdevice when the second irradiator irradiates the interface portion. 15.The abnormality detecting apparatus as set forth in claim 14, whereinthe classifier classifies the appearance failure area into one offailure categories on the basis of at least one of contrasting density,shape, or position of the appearance failure area in the first realimage information and at least one of contrasting density, shape, orposition of the appearance failure area in the second real imageinformation.
 16. The abnormality detecting apparatus as set forth inclaim 1, wherein the obtaining device includes a three-dimensionalmeasurement apparatus for three-dimensionally obtaining the appearanceinformation of the interface portion.
 17. The abnormality detectingapparatus as set forth in claim 1, further comprising a starting deviceconfigured to start the obtaining device at a predetermined timing sothat the obtaining device obtains the appearance information of theinterface portion, or configured to make the failure detector detect theappearance failure of the interface portion at a predetermined timing.18. The abnormality detecting apparatus as set forth in claim 17,further comprising a counting device configured to count a number ofcontacts of the device under test with the interface portion of thecontact arm or to count an occurring number of a predetermined type offailure which occurs in the device under test, wherein the startingdevice starts the obtaining device or makes the failure detector detectthe appearance failure of the interface portion when the counting devicecounts up to a predetermined number.
 19. The abnormality detectingapparatus as set forth in claim 17, further comprising a timing deviceconfigured to measure an elapsed time after starting the test of thedevice under test, wherein the starting device starts the obtainingdevice or makes the failure detector detect the appearance failure ofthe interface portion when the timing device completes measuring apredetermined time duration.
 20. An electronic device testing apparatuscomprising: the contact arm is configured to press the device under testonto a contact portion of a test head; and the abnormality detectingapparatus as set forth in claim
 1. 21. An electronic device testingsystem comprising: a plurality of electronic device testing apparatuseseach having a contact arm and an abnormality detecting apparatusconfigured to detect an abnormality of an interface portion of thecontact arm that contacts the device under test when testing the deviceunder test; and a host computer connected with the electronic devicetesting apparatuses via a communication device, wherein the abnormalitydetecting apparatus comprises: an obtaining device configured to obtainappearance information of the interface portion of the contact arm; afailure detector configured to detect an appearance failure of theinterface portion on the basis of the appearance information obtained bythe obtaining device; and a determining device configured to determinewhether the abnormality occurs at the interface portion on the basis ofa detection result by the failure detector, the determining devicecomprises: a classifier configured to classify the appearance failuredetected by the failure detector into a plurality of failure categorieson the basis of predetermined criteria; a counter configured to count anumber of failures in each of the failure categories and to generate anactual count number for each category; and a comparator configured tocompare the actual count number with a reference count number withrespect to each of the failure categories, and to determine whether theabnormality occurs at the interface portion on the basis of thecomparison result, the reference count number being set in advance as areference number of failures in each of the failure categories, and eachof the electronic device testing apparatuses informs of the actual countnumber generated by the counter to the host computer via thecommunication device in response to a request from the host computer.22. The electronic device testing system as set forth in claim 21,wherein the comparator of the abnormality detecting apparatus determinesthat the abnormality occurs at the interface portion when the actualcount number is larger than the reference count number with respect toat least one of the failure categories.
 23. The electronic devicetesting system as set forth in claim 22, wherein the abnormalitydetecting apparatus comprises an alarm configured to inform that theinterface portion is abnormal or to inform of a failure category whichis a cause for an occurrence of the abnormality at the interface portionwhen the comparator determines that the abnormality occurs at theinterface portion.
 24. An abnormality detecting method for detecting anabnormality of an interface portion of a contact arm of an electricdevice testing apparatus that tests a device under test the interfaceportion contacting the device under test when testing the device undertest, the abnormality detecting method comprising: (a) obtainingappearance information of the interface portion of the contact arm, whenthe interface portion is out of contact with the device under test; (b)detecting an appearance failure of the interface portion of the contactarm on the basis of the appearance information obtained in the (a); and(c) determining whether the abnormality occurs at the interface portionon the basis of a detection result in the (b).
 25. The abnormalitydetecting method as set forth in claim 24, wherein the interface portionincludes a thin-plate-shaped member or a thin-film-shaped memberprovided on a front end portion of the contact arm, or a liquid appliedon the front end portion of the contact arm.
 26. The abnormalitydetecting method as set forth in claim 24, wherein the (c) includes:(c-1) classifying the appearance failure detected in the (b) into aplurality of failure categories on the basis of predetermined criteria;(c-2) counting a number of failures in each of the failure categoriesand generating an actual count number for each category; and (c-3)comparing the actual count number with a reference count number withrespect to each of the failure categories, and determining whether theabnormality occurs at the interface portion on the basis of thecomparison result, the reference count number being set in advance as areference number of failures in each of the failure categories.
 27. Theabnormality detecting method as set forth in claim 26, wherein, in the(c-3), it is determined that the abnormality occurs at the interfaceportion when the actual count number is larger than the reference countnumber with respect to at least one of the failure categories.
 28. Theabnormality detecting method as set forth in claim 26, furthercomprising (d) informing that the interface portion is abnormal orinforming of a failure category which is a cause for an occurrence ofthe abnormality at the interface portion when it is determined that theabnormality occurs at the interface portion in the (c-3).
 29. Theabnormality detecting method as set forth in claim 26, wherein, in the(a), a real image information of the interface portion is obtained bypicking up an image of the interface portion.
 30. The abnormalitydetecting method as set forth in claim 29, wherein, in the (b), an areahaving a predetermined contrast density difference from a background inthe real image information picked up in the (a) is specified as anappearance failure area of the interface portion.
 31. The abnormalitydetecting method as set forth in claim 30, wherein, in the (c-1), theappearance failure area is classified into one of the failure categorieson the basis of at least one of contrasting density, shape, or positionof the appearance failure area specified in the (b).
 32. The abnormalitydetecting method as set forth in claim 29, further comprising (e)memorizing as reference image information of the interface portion, animage information of the interface portion picked up in advance, whereinin the (b), differential image information is generated by performingdifferential processing between the real image information picked up inthe (a) and the reference image information memorized in the (e), and anarea having a predetermined contrast density difference from abackground in the differential image information is specified as theappearance failure area of the interface portion.
 33. The abnormalitydetecting method as set forth in claim 32, wherein, in the (c-1), theappearance failure area is classified into one of the failure categorieson the basis of at least one of contrasting density, shape, or positionof the appearance failure area in the differential image information.34. The abnormality detecting method as set forth in claim 29, whereinin the (a), first real image information is obtained by picking up animage of the interface portion while irradiating the interface portionfrom a first angle, and second real image information is obtained bypicking up an image of the interface portion while irradiating theinterface portion from a second angle different from the first angle,and in the (b), an area having a first contrast density difference froma background in the first real image information and having a secondcontrast density difference from a background in the second real imageinformation is specified as the appearance failure area of the interfaceportion.
 35. The abnormality detecting method as set forth in claim 34,wherein, in the (c-1), the appearance failure area is classified intoone of the failure categories on the basis of at least one ofcontrasting density, shape, or position of the appearance failure areain the first real image information and at least one of contrastingdensity, shape, or position of the appearance failure area in the secondreal image information.
 36. The abnormality detecting method as setforth in claim 29, wherein, in the (a), the interface portion isirradiated with a visible light ray or an ultraviolet ray, and the realimage information of the interface portion is obtained by receiving thevisible light ray or the ultraviolet ray reflected from the interfaceportion.
 37. The abnormality detecting method as set forth in claim 24,wherein, in the (a), the appearance information of the interface portionis three-dimensionally obtained.
 38. The abnormality detecting method asset forth in claim 24, wherein the (a) or the (b) is executed when anumber of contacts of the device under test with the interface portionof the contact arm is equal to or larger than a predetermined number, anoccurring number of a predetermined type of failure which occurs in thedevice under test is equal to or larger than a predetermined number, ora predetermined time duration is elapsed after starting the test of thedevice under test.